عنوان مقاله [English]
In order to further understand the emergence and germination of sugar beet monogerm cultivars under moisture stress, the current study was carried out at three stages. At the first stage, the quality of germination of three monogerm cultivars (Rizofort, Rasoul and Zarghan) were studied under five moisture stress levels (0, -2, -4, -6 and -8 bars) in germinator at 15°C by between-paper method. At this stage, after the onset of the germination, the number of germinated seeds was daily counted and at the end, germination percentage and rate was determined. The second stage was similar to the first one with the difference that at this stage, the percentage of normal and abnormal seedlings was determined 14 days after sowing and then, radicle length, coleoptile length and their ratio as well as radicle and coleoptile dry weight and their ratio were measured for each treatment. At the third stage, the studied cultivars were evaluated in clay soil in growth chamber under moisture stress of 17.5, 20, 22.5 and 25% (control) of soil volumetric moisture. At this stage, when emergence started, the number of emerged seeds was daily counted and then, emergence rate, days to 50% emergence and final emergence percentage were determined for each cultivar and treatment. The statistical design of all stages was a two-factor factorial (the levels of the factors were different at each stage depending on the number of treatments) based on a Randomized Complete Block Design with four replications. The studies were carried out in the laboratories of Agricultural and Natural Resources Research Center of Kermanshah, Iran. Results of the first study showed that moisture stress significantly impacted germination percentage and days to 50% germination, so that as moisture stress was intensified, germination percentage decreased. Also, results revealed that germination percentage of cv. Rizofort was higher than that of Rasoul and Zarghan. Results of the second study indicated that moisture stress significantly affected normal seedlings and ungerminated seeds at 1% probability level. According to the results of the third study too, moisture stress significantly influenced emergence percentage, emergence rate and days to 50% emergence. Results showed that the emergence of sugar beet seeds dramatically decreased at soil volumetric moisture level of lower than 17.5% (-6 bars soil tension) and the emergence percentage of sugar beet seeds did not significantly change with the increase in clay soil volumetric moisture level from 20 to 25% (soil tension of -3 to -0.3 bars).
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